Tips or nibs used in applicators, such as highlighters, pens, cosmetic applicators, and medicament applicators, are typically constructed of felt or thermoplastic fibrous materials including nylon, acrylic, and polyester fibers. Tips or nibs constructed of these materials have good mechanical strength, increasing their resistance to fracture. Moreover, such tips or nibs demonstrate good flow properties of various liquids and have high flexibilities making them suited for use in marking, writing, and other applications.
Several disadvantages, however, exist with felt and fibrous nibs. One disadvantage is the difficulty encountered in producing felt and fibrous nibs having relatively complicated shapes required by various applications. A related disadvantage is that felt and fibrous nibs cannot be produced in a single step. Multi-step production increases costs and places limitations on the various designs felt and fibrous nibs can assume. A further disadvantage is realized upon use of felt and fibrous nibs. Felt and fibrous materials can become frayed and dissociate over the life of the nib. Similarly, fibers can dissolve in the solvent of inks leading to weakening of the nib and further contributing to fraying.
Furthermore, the performance characteristics of applicators comprising felt and fibrous nibs suffer with the deterioration of the felt and fibrous materials. Fraying and other dissociative processes can drastically affect the fineness of an applicator making use thereof difficult and frustrating. Additionally, dissolution of fibers in ink solvents can further complicate matters by leading to excessive ink loss and bleeding.
In view of the foregoing problems and disadvantages, it would be desirable to provide materials demonstrating advantageous mechanical and chemical properties operable to be used as applicators.
Additionally, porous polymeric materials find application and play critical roles in numerous fields. Porous polymeric materials have been widely used in filtration and fluid barrier applications. Current filtration devices often comprise a housing with a polymeric filtration medium disposed in fluid passageways through the housing. As fluid enters the housing, it passes through the filtration medium to remove compositions from the fluid stream. Fluids, as used herein, refer to gases, liquids, or combinations thereof. The efficacy of a filtration device depends on several factors including the ability of the filtration medium to maintain a sufficient seal with the housing to prevent fluid from circumventing the filtration medium.
Fluid circumventing the filtration medium causes significant problems, especially when the filtration medium also serves as a barrier to selected fluids, such as aqueous solutions. Fluid circumventing the filtration medium can contaminate downstream apparatus and processes leading to inconvenience, corrosion and costly repairs of equipment. Pipette devices, for example, often comprise a filtration or barrier medium which allows the passage of fluids such as gasses but prevents the passage of liquids which can contaminate the pipette. Contamination of a pipette by fluids circumventing or bypassing the filtration or barrier medium often requires destruction or decontamination of the pipette due to the potential for subsequent contamination of other solutions.
One disadvantage of present porous polymeric filtration and barrier media is their rigid nature making it difficult to form sufficient seals with housings. This is especially true when either or both the housing and filtration medium have defects resulting from manufacturing or assembly processes. Precise tolerances must therefore be maintained in producing filters comprising filtration media disposed in housings. The requirement of precise tolerances often results in the rejection of a significant amount of product in addition to the potential for the filtration medium to fall out of the housing or otherwise assume an incorrect position within the housing.
In view of the foregoing problems, it would be desirable to provide filtration and barrier media operable to form sufficient seals with housings to prevent fluid bypass without being subjected to the precise tolerances required by present filtration apparatus.